The present invention relates to a ski boot comprising a first component, consisting essentially of a sole and an upper which encloses the foot and the malleolar region, and a second component consisting of a cuff which is articulated with respect to the upper so as to allow the cuff to move from front to rear and vice versa, and means for retaining the cuff which counteract the rearward tilting of the cuff but give way when the force tending to tilt the cuff exceeds a specific value.
The purpose of such a design is to protect the skier's knee, and more precisely the anterior cruciate ligament, when an excessive forward force is exerted on the tibia relative to the femur. It has been observed that tears of the anterior cruciate ligament due to an excessive force of this type have become much more widespread while other types of injury, in particular broken legs and ankles have become much less frequent because of the progress made with safety bindings. Excessive force on the anterior cruciate ligament occurs, in particular, when going over a bump, either when jumping, on landing, or when going down the bump again quickly.
U.S. Pat. No 5,107,608, the content of which is incorporated by reference, has already disclosed a boot equipped with a releasable retaining device intended to protect the anterior cruciate ligament in case of excessive force. This device comprises a latch in the form of a bent lever of the first class which is retained by a spring. In case of excessive force on the cuff, the spring will no longer be capable of retaining the latch, which will tilt and free the cuff. Such a device has the drawback that the skier cannot put it back into its initial position. It is also relatively bulky.
International Patent Application WO 97/22 271, the content of which is incorporated by reference, moreover discloses a ski boot which is also equipped with a retaining device which releases in case of excessive force on the cuff, rearward. This device consists of a sprung linkage, the articulation of which has enough play to allow the articulation pin some degree of longitudinal movement in the lower element of the linkage, and the elements of which abut, at a point lying some distance from the articulation pin, at the end of a travel smaller than the possible displacement of the pin. Once the elements of the linkage have come to abut and the spring of the linkage has already undergone some degree of compression, if the force on the cuff continues to increase then the elements of the linkage will pivot about their bearing point and the linkage will release if its articulation moves beyond alignment of the points of articulation of the linkage to the upper and to the cuff. This device has the advantage that the skier can put it back into its initial position, but it is relatively complex and bulky.
With the aim of protecting the anterior cruciate ligament of the knee, it has also been proposed to introduce a simple spring into a ski boot closure device, joining the rear cuff to the shell of a rear entry boot (European Patent No 0,410,136, the content of which is incorporated by reference). The corresponding published patent application deals with a safety device which opens the closure device of the boot, but the document does not give any examples of embodiments.
Also for a rear entry boot, European Patent Application No 0,514,762, the content of which is incorporated by reference, describes releasable protective devices which are mounted on the front cuff or on the shell and which free a strap or a closure cable of this cuff when pressure on the rear cuff exceeds a specific value.